1. Field of the Invention
The present invention relates to a process for refining base oil, more particularly, to a hydrogenation reaction to obtain white oil from base oil.
2. Description of Related Art
The composition of base oil from petroleum refining process is very complex, and there are many saturated and unsaturated hydrocarbons with nitrogen and sulfur compounds making the base oil look yellow. Consequently, a decolorizing process is usually used to obtain white oil. The conventional decolorizing process includes an oleum/clay method and a hydrogenation method. The quality of white oil obtained by the oleum/clay method is not so good, and the acid in the reaction is not easy to process and can easily pollute the environment. So many companies do not use this method to produce white oil gradually.
The other method, the hydrogenation method, does not have the same drawbacks as the oleum/clay method. In the hydrogenation method, base oil is fed in liquid state into a reactor and hydrogen is continuously pumped into the reactor. Base oil is fed into the reactor through an inlet above the reactor. The reaction is controlled by the mass transfer resistance of the vapor/liquid phase and liquid/solid phase so the reaction must be carried out at high temperature (about 250xcx9c380xc2x0 C.) and high pressure (xcx9c3000 psi). The mass transfer resistance also makes the reaction more difficult, and the cost of equipment to obtain white oil is higher.
The objective of the present invention is to provide a process for the production of white oil.
To achieve the objective, the present invention comprises injecting a supercritical fluid into the reactor with the base oil and hydrogen. Injecting the supercritical fluid will result in homogeneous of reaction phase and reduction of the mass transfer resistance between the reactant and the catalyst, the film resistance of the catalyst surface and the diffusion resistance of catalyst holes. The supercritical fluid can also reduce the coke formation, which allows the catalyst to run longer. If the reaction productivity keeps the same as the conventional method, addition of the supercritical fluid will reduce the pressure or the temperature of the reaction.
Other objectives, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.